Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752793AbaLFPKf (ORCPT ); Sat, 6 Dec 2014 10:10:35 -0500 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:47796 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752356AbaLFPIM (ORCPT ); Sat, 6 Dec 2014 10:08:12 -0500 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Kees Cook , Andy Lutomirski , Toshi Kani , Yasuaki Ishimatsu , David Vrabel , Wang Nan , Yinghai Lu , Thomas Gleixner , Jiri Slaby Subject: [PATCH 3.12 17/66] x86, mm: Set NX across entire PMD at boot Date: Sat, 6 Dec 2014 16:07:09 +0100 Message-Id: <868b19cb0314da9725ec108ec6abb082965cd0c2.1417878427.git.jslaby@suse.cz> X-Mailer: git-send-email 2.1.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kees Cook 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 45e2a9d4701d8c624d4a4bcdd1084eae31e92f58 upstream. When setting up permissions on kernel memory at boot, the end of the PMD that was split from bss remained executable. It should be NX like the rest. This performs a PMD alignment instead of a PAGE alignment to get the correct span of memory. Before: ---[ High Kernel Mapping ]--- ... 0xffffffff8202d000-0xffffffff82200000 1868K RW GLB NX pte 0xffffffff82200000-0xffffffff82c00000 10M RW PSE GLB NX pmd 0xffffffff82c00000-0xffffffff82df5000 2004K RW GLB NX pte 0xffffffff82df5000-0xffffffff82e00000 44K RW GLB x pte 0xffffffff82e00000-0xffffffffc0000000 978M pmd After: ---[ High Kernel Mapping ]--- ... 0xffffffff8202d000-0xffffffff82200000 1868K RW GLB NX pte 0xffffffff82200000-0xffffffff82e00000 12M RW PSE GLB NX pmd 0xffffffff82e00000-0xffffffffc0000000 978M pmd [ tglx: Changed it to roundup(_brk_end, PMD_SIZE) and added a comment. We really should unmap the reminder along with the holes caused by init,initdata etc. but thats a different issue ] Signed-off-by: Kees Cook Cc: Andy Lutomirski Cc: Toshi Kani Cc: Yasuaki Ishimatsu Cc: David Vrabel Cc: Wang Nan Cc: Yinghai Lu Link: http://lkml.kernel.org/r/20141114194737.GA3091@www.outflux.net Signed-off-by: Thomas Gleixner Signed-off-by: Jiri Slaby --- arch/x86/mm/init_64.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 104d56a9245f..b599241aea81 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1110,7 +1110,7 @@ void mark_rodata_ro(void) unsigned long end = (unsigned long) &__end_rodata_hpage_align; unsigned long text_end = PFN_ALIGN(&__stop___ex_table); unsigned long rodata_end = PFN_ALIGN(&__end_rodata); - unsigned long all_end = PFN_ALIGN(&_end); + unsigned long all_end; printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n", (end - start) >> 10); @@ -1121,7 +1121,16 @@ void mark_rodata_ro(void) /* * The rodata/data/bss/brk section (but not the kernel text!) * should also be not-executable. + * + * We align all_end to PMD_SIZE because the existing mapping + * is a full PMD. If we would align _brk_end to PAGE_SIZE we + * split the PMD and the reminder between _brk_end and the end + * of the PMD will remain mapped executable. + * + * Any PMD which was setup after the one which covers _brk_end + * has been zapped already via cleanup_highmem(). */ + all_end = roundup((unsigned long)_brk_end, PMD_SIZE); set_memory_nx(rodata_start, (all_end - rodata_start) >> PAGE_SHIFT); rodata_test(); -- 2.1.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/